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list_nodes

Read-onlyIdempotent

Fetch the ROS 2 graph's nodes in a single read-only CLI call, returning name, namespace, full_name, and duplicate_count for each; empty if none exist.

Instructions

ROS 2 graph only; on a DDS-only setup use list_participants. List the nodes on the ROS 2 graph (or the mock graph) from one ros2 node list call as a NodeListing: name, namespace, full_name, duplicate_count. duplicates lists full names used by several nodes (a per-node tool then answers for one of them, unidentified). Nodes starting with an underscore are hidden and a node on another ROS_DOMAIN_ID is invisible. Empty nodes when the graph has none. Use get_node_info for one node's interfaces. Raises an MCP error without a ros2 CLI. Read-only; cheap (one CLI call). Duration: runs the ros2 CLI behind the ROS lock (one call at a time); the whole call, lock wait included, ends within 45 s, and if another ros2 call holds the lock it fails at once with a busy error (retry).

Input Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Output Schema

TableJSON Schema

Name	Required	Description
`note`	No	One sentence of context, or `None`.
`nodes`	Yes	Nodes on the graph, one entry per distinct full name, sorted by name.
`total`	Yes	Distinct node names on the graph (no cap applies).
`returned`	Yes	Length of `nodes`.
`truncated`	Yes	True when `returned` is less than `total` because of a cap.
`duplicates`	Yes	Full names that appear more than once on the graph. Empty when every name is unique.
`mode_effective`	Yes	`live` or `mock` (fixtures).

Schema Changelog

Changes observed during successful MCP inspections.

Addedv0.7.1Oct 14, 2026

TDQS

A4.8/5.0

Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), and the description adds genuinely new behavior: empty `nodes` on an empty graph, an MCP error without the `ros2` CLI, hidden underscore-prefixed nodes, cross-ROS_DOMAIN_ID invisibility, and the lock semantics (45 s ceiling, immediate `busy` error to retry). These are runtime traits the annotations cannot express.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded with the disambiguating scope clause before any detail, and each sentence carries distinct information (routing, return shape, edge cases, error/duration behavior). It is dense and bold-heavy, but nothing reads as filler.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With an output schema present the description need not detail return values, yet it still flags the key semantic of `duplicates` and the empty-graph case. Combined with explicit failure modes (missing CLI, lock contention) and the sibling routing hint, an agent has everything needed to call this correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The tool takes zero parameters, so the baseline is 4; there is nothing for the description to clarify. Its explanation of return fields (`duplicates`, `full_name`) goes beyond parameters, which is bonus context rather than parameter semantics.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ('List the nodes on the ROS 2 graph') plus the data source ('one `ros2 node list` call') and the returned shape (`NodeListing` with name, namespace, full_name, duplicate_count). The opening clause immediately distinguishes it from `list_participants` for DDS-only setups, so an agent can route between the two without opening either schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives explicit when-to-use routing: 'ROS 2 graph only; on a DDS-only setup use `list_participants`' and 'Use `get_node_info` for one node's interfaces'. It also names the conditions that change behavior (mock graph, no ros2 CLI, busy lock) so the agent knows when this call will succeed or fail.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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